Not applicable.
Not applicable.
The present invention relates to satellite beam patterns. In particular, the present invention relates to overlapping beam patterns that support the bandwidth requirements of non-uniform population distributions.
Satellites carry antenna that provide communications bandwidth between the satellite and a region of interest (ROI). The ROI, for example, may include the entire United States, or any other selected portion of the Earth. Because many ROIs, including the United States, have a non-uniform population distribution, it is often the case that areas of a particular size within the ROI have much greater bandwidth requirements than equal sized areas elsewhere within the ROI.
In the past, however, satellite antennae have either produced a single beam which covers an entire ROI, or have produced a set of equal sized beams laid out on a regular grid pattern to cover the ROI. The past approaches to beam coverage have a number of undesirable characteristics. First, the bandwidth provided by the beam coverage may not be adequate for areas of high bandwidth demand (generally corresponding to areas of high population density). Thus, suppliers of communications services, for example, Internet service providers or cable TV operators in a particular Nielsen region, cannot establish accounts with consumers who might be willing to pay for those services. Similarly, the bandwidth provided by the beam coverage may greatly exceed the bandwidth need in sparsely populated regions. As a result, bandwidth which may be needed elsewhere is wasted.
Furthermore, when a grid pattern is used, the portion of the frequency spectrum (typically selected from the K or C frequency bands) occupied by the beams simply alternates across the grid. As a result, prior beam patterns require transmitting the same information on several beams to cover a wide area. For example, in the West, a particular market region may be much larger than a single beam. The same information must, therefore, be transmitted on several beams that cover the market region. As a result, the amount of bandwidth provided in a grid pattern may be more than twice the amount actually necessary to support the total bandwidth demand.
The inability of prior antenna to produce efficient beam coverage for non-uniform populations is a result of beam pattern design tradeoffs including antenna size, coverage area, and power limitations. Production of smaller, tightly focused beams for densely populated areas, sometimes referred to as spot beams, requires a very large antenna. Very large antennas, in turn, are expensive to manufacture and launch, and require more power during operation the most conventional satellites can generate. On the other hand, a smaller antenna may be used to produce a larger beam, but the larger beam cannot focus its bandwidth on a small area of high bandwidth demand.
As a result, it is desirable to project a beam pattern on the ROI which uses numerous beams of various sizes to provide the appropriate bandwidth for each area in the ROI. In other words, a set a tightly focused beams (referred to as xe2x80x9cspot beamsxe2x80x9d) might be directed towards areas of high bandwidth density, while a smaller set (or even a single beam) of less tightly focused beams might be appropriate for a much larger area with a lower bandwidth demand (for example, some of the sparsely populated Western states). Directing the appropriate amount of bandwidth to the appropriate areas results in less expensive, more efficient, and less complex beam pattern coverage. Appropriate beam pattern coverage also tends to create more communications services available at a lower cost to more individuals.
Therefore, a need remains for improved antenna beam patterns which overcome the disadvantages discussed above and previously experienced.
It is therefore an object of the present invention to provide antenna beam pattern coverage for a ROI with a non-uniform population distribution.
It is another object of the present invention to provide spot beams for areas of relatively high bandwidth demand while providing wider beams for areas of relatively low bandwidth demand.
It is another object of the present invention to provide the bandwidth requirements for a ROI with fewer beams.
It is yet another object of the present invention to provide beam pattern coverage that is not constrained to a regular grid pattern.
It is another object of the present invention to provide overlapping beams of differing sizes to cover a ROI of non-uniform population distribution.
The present invention is directed toward a method for providing antenna beam pattern coverage for a region of interest having a non-uniform population distribution. At least one first set of beams is generated. Each of the first beams shares a common size that determines the area of coverage for each of the first beams when projected onto the ROI. Each of the beams in the first set of beams is allocated a portion of the electromagnetic spectrum which need not be unique among each of the beams in the first set of beams. For example, a portion of the frequency spectrum 1 GHz in width may be divided into six portions approximately 166 MHz wide and each portion may then be reused among the beams in the first set of beams.
At least one set of second beams is also generated. In the same fashion as the first beams, each of the second beams shares a common size that determines the area of coverage for each of the second beams when projected onto the ROI. Each of the beams in the second set of beams is allocated a portion of the electromagnetic spectrum which need not be unique among each of the beams in the second set of beams. For example, a portion of the frequency spectrum 1 GHz in width may be divided into six portions approximately 166 MHz wide and each portion may then be reused among the beams in the second set of beams.
In order to provide coverage for the ROI, the first and second beams are projected, for example, by a satellite antenna, onto the region of interest. The projection of the beams is arranged such that each of the first beams and each of the second beams is substantially non-interfering with any adjacent beam. In other words, the projection is designed initially so that where any two beams may overlap, those two beams occupy unique portions of the electromagnetic spectrum and are therefore non-interfering.
In additional to assigning unique portions of the electromagnetic spectrum to beams, the invention also comprehends creating polarized beams. Two beams occupying the same unique portion of the electromagnetic spectrum may then overlap without interfering provided that the polarizations on the overlapping beams are opposite or otherwise non-interfering.